Handle idle PostgreSQL client errors

web/lib/db.test.ts

@@ -232,6 +232,14 @@ describe('createPool threads idleTimeoutMillis into the pg Pool (via getPool)',
   ] as const;
   const saved: Record<string, string | undefined> = {};
 
+  function configurePoolEnvironment(): void {
+    process.env.BENCH_DB_HOST = 'localhost';
+    process.env.BENCH_DB_NAME = 'bench';
+    process.env.BENCH_DB_USER = 'bench_reader';
+    process.env.BENCH_DB_PASSWORD = 'fixture-pw';
+    process.env.BENCH_DB_SSL = 'disable';
+  }
+
   beforeEach(async () => {
     for (const k of ENV_KEYS) saved[k] = process.env[k];
     await resetPool();
@@ -246,11 +254,7 @@ describe('createPool threads idleTimeoutMillis into the pg Pool (via getPool)',
   });
 
   it('uses the resolved timeouts as pool options', () => {
-    process.env.BENCH_DB_HOST = 'localhost';
-    process.env.BENCH_DB_NAME = 'bench';
-    process.env.BENCH_DB_USER = 'bench_reader';
-    process.env.BENCH_DB_PASSWORD = 'fixture-pw'; // skips the IAM/Signer path
-    process.env.BENCH_DB_SSL = 'disable'; // avoids the BENCH_DB_CA requirement
+    configurePoolEnvironment();
     process.env.BENCH_DB_IDLE_TIMEOUT_MS = '123456';
     process.env.BENCH_DB_STATEMENT_TIMEOUT_MS = '23456';
 
@@ -262,6 +266,17 @@ describe('createPool threads idleTimeoutMillis into the pg Pool (via getPool)',
     expect(pool.options.idleTimeoutMillis).toBe(123456);
     expect(pool.options.statement_timeout).toBe(23456);
   });
+
+  it('handles idle-client errors on the shared pool', () => {
+    configurePoolEnvironment();
+    const pool = getPool();
+    const error = new Error('fixture idle-client disconnect');
+    const log = vi.spyOn(console, 'error').mockImplementation(() => {});
+
+    expect(pool.listenerCount('error')).toBe(1);
+    expect(() => pool.emit('error', error)).not.toThrow();
+    expect(log).toHaveBeenCalledWith('bench: idle PostgreSQL client error', error);
+  });
 });
 
 describe('requireEnv', () => {

web/lib/db.ts

@@ -173,7 +173,7 @@ export function passwordProvider(config: DbConfig): () => Promise<string> {
 }
 
 function createPool(config: DbConfig = readConfig()): Pool {
-  return new Pool({
+  const pool = new Pool({
     host: config.host,
     port: config.port,
     database: config.database,
@@ -184,6 +184,13 @@ function createPool(config: DbConfig = readConfig()): Pool {
     idleTimeoutMillis: config.idleTimeoutMillis,
     statement_timeout: config.statementTimeoutMillis,
   });
+  // pg emits idle-client connection failures on the pool. Without this
+  // listener, EventEmitter turns a recoverable disconnect into an uncaught
+  // exception. The pool removes the failed client and replaces it on demand.
+  pool.on('error', (error) => {
+    console.error('bench: idle PostgreSQL client error', error);
+  });
+  return pool;
 }
 
 // A single pool is shared across warm serverless invocations and survives